The present invention relates generally to wireless communication networks and, in particular, to reliably communicating information packets in such networks so as to account for bursts of unplanned interference.
Wireless communication networks are known and come in a variety of forms. Notable networks include cellular telephone networks, classic land mobile radio networks and satellite transmission networks. These networks are typically characterized as wide area networks. More recently, wireless local area networks and wireless home networks have been proposed, and standards, such as Bluetooth and IEEE 802.11, have been introduced to govern the development of wireless equipment for such localized networks.
Most wide area networks operate using licensed frequencies that have been allocated for such use by a governmental agency, such as the United States Federal Communications Commission. Consequently, network designers and planners can use conventional system planning software tools to predict interference patterns and design their systems to mitigate the effects of interference (e.g., through appropriate selection of reuse patterns and propagation modeling).
By contrast, proposed wireless home networks will use unlicensed frequency spectrum most likely in the newly opened five Gigahertz (5 GHz) frequency range. Consequently, each wireless home network has the possibility of encountering substantial, unpredictable interference due to the presence of neighboring home networks (e.g., in apartment buildings, condominiums, and town homes) operating on common frequencies. Adding further to the complexity of wireless home networks, such networks will likely be required to support real-time information, such as audio and video services, in such a manner that users of the networks cannot notably distinguish the reception of real-time information (e.g., a cable television signal or a cordless telephone signal) over a wireless home network from the reception of such information over a typical wired or cabled network. In other words, users of wireless home networks will expect the same quality of service with wireless home networks as they currently receive from their wired networks. The provision of such quality of service is rendered quite difficult in an environment of unpredictable interference that can unexpectedly corrupt transmitted information.
Various methods exist for reliably communicating information in wireless networks. Wide area data networks commonly utilize automatic repeat request (ARQ) or selective ARQ (SARQ) schemes in which a transmitting device retransmits unacknowledged or negatively acknowledged data packets or portions thereof to a receiving device over a traffic channel assigned for the data communication in the event that the data packets or the data packet portions are received with errors by the receiving device. While such schemes do provide a mechanism for insuring reliable communications, they also introduce delays that are unacceptable for the transmission of real-time information because retransmission under an ARQ or SARQ scheme requires a temporary stoppage or interruption in the transmission of the data stream. If applied to the transmission of real-time information, such stoppages would produce user-noticeable aberrations in the received information stream (e.g., silence in an audio transmission or jitter in a video transmission), likely resulting in user discontent.
Some cellular networks allocate a group of secondary traffic channels in each cell for emergency use in the event that the signal qualities of primary traffic channels degrade significantly during voice calls. In such networks, when the signal quality of a primary traffic channel degrades to such a degree that the system controller would ordinarily drop or terminate the call, the system controller attempts to re-assign the call to one of the secondary traffic channels. If a secondary channel is available, the system controller re-assigns the call to the secondary channel and the call continues; otherwise, the call is dropped or terminated. In either event, the primary traffic channel is de-allocated and becomes available for a new call. While the allocation and use of a secondary traffic channel facilitates continuation of the call, it does not insure the reliability of the transmitted information. That is, any information that is lost during the transition from the primary traffic channel to the secondary traffic channel is never recovered.
Therefore, a need exists for a method and apparatus for reliably communicating information packets in a wireless communication network that facilitate the transmission of real-time information, without introducing undesirable delays that could negatively impact the high quality of service typically expected by users of such information.